192 SUMMARY OF CURRENT RESEARCHES RELATING TO 



B, INVERTEBRATA. 



Mollusca. 



Development of Reproductive Organs of Pulmonate Mollusca.* 

 — H. Eouzaud finds that the reproductive organs of the Pulmonata 

 arise from an ectodermic bud, which is primitively simple and clavi- 

 form, and which he calls the primitive bud. The hermaphrodite gland 

 is merely the free ramified apex of this bud. The bud itself is formed 

 by the cutaneous envelope in the region which separates the head 

 from the pallial " collar," and always arises at the spot at which the 

 common or the female orifice is afterwards developed. At first clavi- 

 form, it becomes cylindrical, and, following the general integument, 

 soon extends to the level of the liver. Its basal region soon gives rise 

 to a secondary bud, the rudiment of the penis, of the male efferent 

 canal, and of the flagellum. At its free end this bud soon presents a 

 tract of muscular tissue which is connected with the wall of the body, 

 and is the representative of the future retractor muscle of the penis. 

 Inferiorly to this, there is developed another bud — the sagittal — 

 which is the rudiment of the dart-sac. In a large number of so-called 

 Helices the base of the sagittal bud also proliferates and gives rise to 

 a certain number of tertiary buds which form the glands or multifid 

 vesicles ; these should, however, be regarded as parts of the dart-sac. 

 The median region now presents two clefts, which are distinguished 

 as the utero-copulative, and the utero-deferent. With the former 

 there becomes connected the copulatory pouch, and with the latter 

 the oviduct. The arrangement of the parts are such that the dart 

 and the " copulatory cellular layer " are the symmetrical homologues 

 of the penis and the efferent canal. 



There are, then, three tracts of cells ; the median one, which is 

 the oviduct, gives rise to the albuminiparous gland. While these 

 changes have been going on, the tip of the primitive bud has been 

 actively proliferating, and has given rise to a number of rudimentary 

 lobules of the hermaphrodite gland. The sexual products would 

 appear to be derived from the ectoderm. 



Developmental History of the Prosobranchiata.t — Dr. Carl 

 Eabl's memoir is divided into two parts — the first treating of the 

 question of the ultimate fate of the gastrula-mouth in Paludina 

 vivipara, while the second relates to some later developmental pro- 

 cesses in Bythinia tentaculata. 



The question of the fate of the gastrula-mouth is of great 

 theoretical importance ; and there is at present scarcely a point in 

 developmental history about which there has been more dispute, and 

 upon which opinions are more divided. The author finds that in 

 Paludina vivipara the gastrula-mouth gradually but completely closes 

 in the median line of the ventral surface ; that, further, soon after 

 its closure the anus makes its appearance, but is in no way connected 

 with the gastrula-mouth ; and that, lastly, the permanent mouth 



* Comptcs Eeiuliis, xcvi. (1883) pp. 273-6. 



t Anzeig. Akad. Wiss. Wien, Jan. 18, 1883, p. 13. 



